Power line carrier (PLC) is a special communication mode of power system. Power line carrier communication refers to the technology of high-speed transmission of analog or digital signals by using existing power lines. The biggest feature is that there is no need to rebuild the network, as long as there are wires, data can be transferred.
However, due to the following disadvantages of PLC, the main application of PLC - "power grid" has not been applied on a large scale
1. The distribution transformer can block the power carrier signal, so the power carrier signal can only be transmitted in one distribution transformer area;
2. There is a large signal loss (10 dB - 30 dB) between three-phase power lines. When the communication distance is very close, different phases may receive signals. Generally, power line carrier signal can only be transmitted on single-phase power line;
3. The loss of power carrier signal is different in different signal coupling modes, such as wire ground coupling and wire neutral coupling. Compared with the line neutral coupling mode, the line ground coupling mode can reduce the power carrier signal loss by more than 10 dB, but the line ground coupling mode is not suitable for all regional power systems;
4. The power line has its own pulse interference. At present, there are 50 Hz and 60 Hz alternating current, and the cycle is 20 ms and 16.7 Ms. in each AC cycle, there are two peaks, and the two peaks will bring two pulse interference, that is, there is a fixed 100 Hz or 120 Hz pulse interference on the power line, and the interference time is about 2 ms, so the interference must be dealt with. There is a method of using waveform to transmit data in a short time after zero point, but because of the short time after zero point, it is difficult to control the synchronization between practical application and AC waveform, and the modern communication data frame is relatively long, so it is difficult to apply;
5. The power line causes high reduction of carrier signal. When the load on the power line is very heavy, the line impedance can be less than 1 ohm, resulting in a high reduction of the carrier signal. In practical application, when the power line is unloaded, the point-to-point carrier signal can be transmitted to several kilometers. But when the load on the power line is very heavy, it can only transmit tens of meters.
Although the technical problems can be solved and overcome with the development of time, the time and space left for PLC is not abundant from the current situation of domestic broadband network construction. Since 2000, the major operators have launched a variety of broadband access services, such as ADSL, optical fiber, wireless network and so on. The living space left for power line access has been compressed by other access methods. Now, in addition to the application of PLC in remote meter reading, there is no original heroic words.
With the rise of the topic of home intelligent system, it also brings a new stage to PLC. In the current home intelligent system, the PC based home intelligent system is the most popular. The concept of the system is that with the popularity of computers, all the data that household appliances need to process can be handed over to the computer to complete. In this way, we need to build a data transmission network between home appliances and PC. now everyone is optimistic about wireless, but in the home environment, the feature of "more walls" seriously affects the quality of wireless transmission, especially in villas and jump floor houses. If you set up a dedicated cable network, in addition to increasing costs, then the location of home appliances can not be moved at will in the future.
The biggest feature of PLC: no need to re set up the network, as long as there are wires, it can carry out data transmission, which undoubtedly becomes one of the best solutions to solve the problem of smart home data transmission. At the same time, because the data is only transmitted in the family, the five problems that restrict the application of PLC will no longer exist. We can also realize the remote control of home appliances by connecting to the PC first through the traditional network and then controlling the home appliances. The cost of PLC modulation and demodulation module is far lower than that of wireless module.